use scrubbing bubbles, got the idea from bmw forum.
Since its bmw, they wont use crazy sh!t towards their engine unless they know it works. enjoy. I take out the positive, tape it up, cover the alternator, and i spray it like how i spray the toilet bowl. All over. Let it sit and mist it with the water hose.
Crank the car up, drive around. All the heat will evaporate everything else.